MYP Chemistry Ionic Bonding and Ionic Compounds International College Spain.
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Transcript of MYP Chemistry Ionic Bonding and Ionic Compounds International College Spain.
MYP ChemistryIonic Bonding and Ionic
Compounds
International College Spain
Electron Configuration in Ionic Bonding
OBJECTIVES:
–Use the periodic table to infer the number of valence electrons in an atom, and draw it’s electron dot structure.
Electron Configuration in Ionic Bonding
OBJECTIVES:
–Describe the formation of cations (positive ions) from metals, and of anions (negative ions) from non-metals.
Valence Electrons The electrons responsible for the
chemical properties of atoms are those in the outer energy level.
Valence electrons - The electrons in the outer energy level or shell
–the highest occupied energy level Inner electrons -those in the energy
levels below.
Keeping Track of Electrons Atoms in the same column...
–Have the same outer electron configuration.
–Have the same valence electrons. Easily found: same as the main group
number on the periodic table. Group 2A: Be, Mg, Ca, etc.
–2 valence electrons
Electron Dot diagrams A way of keeping track of
valence electrons. How to write them? Write the symbol. Put one dot for each
valence electron Don’t pair up until they
have to.
X
The Electron Dot diagram for Nitrogen
Nitrogen has 5 valence electrons.
First we write the symbol.
NThen add 1 electron at a time to each side.Until they are forced to pair up.
Write electron dot diagrams: Na Mg C O F Ne
Electron Configurations for Cations
Metals lose electrons to attain noble gas configuration.
They make positive ions (cations) If we look at the electron configuration,
it makes sense to lose electrons: Na 2,8,1 1 valence electron Na+ 2,8 noble gas configuration
Electron Dots For Cations Metals will have few valence
electrons (usually 3 or less)
Ca
Electron Dots For Cations Metals will have few valence electrons These will come off
Ca
Electron Dots For Cations Metals will have few valence electrons These will come off Forming positive ions
Ca2+Now make Sc an ion.
Pseudo-noble gas configuration
Electron Configurations for Anions
Nonmetals gain electrons to attain noble gas configuration.
They make negative ions (anions) Halide ions- ions from chlorine or other
halogens that gain electrons S 1s22s22p63s23p4 6 valence electrons S2- 1s22s22p63s23p6 noble gas
configuration.
Electron Dots For Anions Nonmetals will have many valence
electrons (usually 5 or more) They will gain electrons to fill outer shell.
P P3-
Stable Electron Configurations All atoms react to achieve noble gas
configuration. Noble gases have 8 outer shell
(valence) electrons. Also called the octet rule.
Ar
Ionic Bonds
The characteristics of an ionic
bond.
Ions held together by……..
electrostatic attraction
Ionic Bonds Characteristics of ionic compounds electrical conductors when melted
and when in aqueous solution. High m.p. Brittle, hard crystals
Properties of ionic compounds You are provided with three ionic
compounds For each carry out the following tests
1. Heat a sample strongly in a test tube.
2. Add a spatula of the compound to 25 cm3 of water in a small beaker- stir
3. Test the conductivity of the solution
Repeat using two spatulas
Ionic Bonding Anions and cations are held
together by opposite charges. Ionic compounds are called salts. Simplest ratio is called the formula
unit. The bond is formed through the
transfer of electrons. Electrons are transferred to achieve
noble gas configuration.
Ionic Bonding
Na Cl
Ionic Bonding
Na+ Cl-
Ionic Bonding All the electrons must be accounted for
Ca P
Ionic Bonding
Ca P
Ionic Bonding
Ca2+ P
Ionic Bonding
Ca2+ P
Ca
Ionic Bonding
Ca2+ P 3-
Ca
Ionic Bonding
Ca2+ P 3-
Ca P
Ionic Bonding
Ca2+ P 3-
Ca2+ P
Ionic Bonding
Ca2+ P 3-
Ca2+ P
Ca
Ionic Bonding
Ca2+ P 3-
Ca2+ P
Ca
Ionic Bonding
Ca2+ P 3-
Ca2+P
3-
Ca2+
Ionic Bonding
= Ca3P2Formula Unit
Calcium Phosphide
Classwork problems (a)Show the bonding between the following
1. Magnesium and Oxygen
2. Potassium and Chlorine
3. Calcium and Fluorine
4. Lithium and Nitrogen
5. Aluminium and Fluorine
Homework problemsThese are slightly harder
6. Magnesium and Phosphorus
7. Beryllium and Nitrogen
8. Calcium and Sulphur
9. Magnesium and Nitrogen
10. Aluminium and Oxygen
Properties of Ionic Compounds Crystalline structure, usually solids A regular repeating arrangement of
ions in the solid Ions are strongly bonded together. Structure is rigid. High melting points Electrical conductors when melted Electrical conductors in solution
Crystalline structure
Do they Conduct? Conducting electricity is allowing charges
to move. In a solid, the ions are locked in place. Ionic solids are insulators. When melted, the ions can move around. Melted ionic compounds conduct.
– NaCl: must get to about 800 ºC. Dissolved in water they conduct (aqueous)
Bonding in Metals
OBJECTIVES:
–Use the theory of metallic bonds to explain the physical properties of metals.
Bonding in Metals
OBJECTIVES:
–Describe the arrangements of atoms in some common metallic crystal structures.
Metallic Bonds How atoms are held together in the
solid. Metals hold on to their valence
electrons very weakly. Think of them as positive ions
(cations) floating in a sea of electrons:
Sea of Electrons
+ + + ++ + + +
+ + + +
Electrons are free to move through the solid.
Metals conduct electricity.
Metals are Malleable Hammered into shape (bend). Also ductile - drawn into wires. Both malleability and ductility
explained in terms of the mobility of the valence electrons
Malleable
+ + + ++ + + +
+ + + +
Malleable
+ + + +
+ + + ++ + + +
Electrons allow atoms to slide by.
Ionic solids are brittle
+ - + -+- +-
+ - + -+- +-
Ionic solids are brittle
+ - + -
+- +-+ - + -
+- +-
Strong Repulsion breaks crystal apart.
Crystalline structure of metal If made of one kind of atom,
metals are among the simplest crystals
1. Body-centered cubic:
– every atom has 8 neighbors
– Na, K, Fe, Cr, W
Crystalline structure of metal2. Face-centered cubic:
–every atom has 12 neighbors
–Cu, Ag, Au, Al, Pb
3. Hexagonal close-packed
–every atom also has 12 neighbors
–different pattern due to hexagonal
–Mg, Zn, Cd
Alloys We use lots of metals every day,
but few are pure metals Alloys - mixtures of 2 or more
elements, at least 1 is a metal made by melting a mixture of the
ingredients, then cooling Brass: an alloy of Cu and Zn Bronze: Cu and Sn
Why use alloys? Properties often superior to element Sterling silver (92.5% Ag, 7.5% Cu)
is harder and more durable than pure Ag, but still soft enough to make jewelry and tableware
Steels are very important alloys
–corrosion resistant, ductility, hardness, toughness, cost
Why use alloys? Look up alloys in your text book Types? a) substitutional alloy- the
atoms in the components are about the same size
b) interstitial alloy- the atomic sizes quite different; smaller atoms fit into the spaces between larger
Amalgam- dental use, contains Hg